#include <stdio.h>

int main()
{
    int arr[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
    int n = 0;
    scanf("%d",&n);
    int sz = sizeof(arr) / sizeof(arr[0]);
    int left = 0;
    int right = sz - 1;
    while(left <= right)
    {
        int mid = (right + left) / 2;
        if(arr[mid] > n)
        {
            right = mid - 1;
        }
        else if(arr[mid] < n)
        {
            left = mid +1;
        }
        else
        {
            printf("找到了，下标为%d\n",mid);
            break;
        }
    }   
    if(left > right)
    {
        printf("没找到\n");
    }
    
    return 0;
}